1. Field of the Invention:
This invention relates generally to improvements in apparatus for thermal management of electronic modules, and more particularly relates to a self-adjusting heat transfer system for temperature control and automatic clamping of electronic modules.
2. Prior Art:
Temperature control of electronic modules, particularly in advanced avionics systems, can pose a problem when there is high power consumption and high heat production from circuit cards that have electronic components mounted in a high density configuration. A high efficiency heat removal system is often neccesary in order to provide a proper temperature environment in the range of about 20.degree. to 1OO.degree. C.
Air cooling systems which force air across the modules or draw air around the modules have been used in the past. However, circulation of a liquid coolant to cool the modules is often a more efficient method of heat removal. Such systems typically route a liquid coolant through cavities in the interior of cold plates that support circuit card racks which hold the modules, with means for communicating heat from the electronic components to the racks. Heat pipes mechanically clamped to the circuit card rack, and flexible wall or pressurized bellows-type cooling plates bearing against an edge of a circuit card rack have been used for communicating heat from the electronic components. Internal heat pipes in the body of the circuit card, in close thermal communication with the electronic components on the card, and in thermal communication with the ends of the circuit card body, are also known. While these devices have served their purpose, there remains a continuing desire for further improvements in terms of a device which is simpler in construction, more efficient at thermal management, and designed to provide a shorter thermal path between the module and the coolant.
It has also been known that thermal resistance at the interface between two bodies having different temperatures is dependent upon the contact pressure at the interface. The thermal conductivity increases, and the thermal resistance decreases, as the contact pressure increases at the interface. It would therefore be desirable to provide an interface for electronic modules that decreases the thermal resistance of the interface.
Breakage of modules has also been a problem. Often the electrical and mechanical connections in the circuit card rack are configured in a way which makes it difficult to install the cards in the rack or remove them from the rack without applying substantial force. Cards have been known to break or be damaged when subjected to this force, resulting in increased expense and prolonged system down-time. It would be desirable to provide an automatic clamping mechanism to lock circuit card modules into the rack during operation, and to automatically unclamp them during non-operation, so as to allow easy removal and insertion of the modules for routine maintenance and assembly procedures. The present invention fulfills all of these needs.